Coated article



April 23, 1946. M. BROWN ErAL 2,398,881

COATED ARTICLE Original Filed May"20, 1939 /N vE/vro/es- M.A BEow/v Patented pr'. 23, 1946 irse srAfrss PATENT. osi-*lcs cos'rsn Annota l l y l Mon-n Bgm, western spring, ma ami n. Barr, Downers Grove, Ill., asignan to Western Electric Company, Incorporated, New York, N. Y.,-a corporation o! New York 4 I riginal application May 20, 1939,' Serial No.

274,750; Divided and this application 1944, Serial No. 539,284

This invention relates to enamel coated articles and to methods of making enamel coated articles, and this application is a division of our copending application Serial No. 274,750, filed May 20, 193g, now Patent 2,377,321, granted June 5, 1945.

Objects of the invention are the production of articles having a highly ornamental and serviceable enamel coating, and the 'provision of. efdcient and economical methods for making such articles. v

The invention is particularly adapted to the production of enameled articles such as the number plates which are incorporated in telephone dials. These plates comprise a metal base with a coating of vitreous enamel on the portions of the base that'are exposed in the dial assembly. A highly adherent -enamel coating is required to withstand rough usage land it is especially deslry 'e able to provide a particularly smooth. even and unbroken surface on the enamel. The plates are yoiten exposed to dirt-laden atmospheres in servl ice and under these conditions even-minute imperfections in the enamel surface .may accumulate dust, dirt, lint and the like. These foreign materials are diiilcult to remove from surface cracks and pits, and the plate very soon becomes l unsightly if any of these defects are present. Certain types of number plates receive a multi-color iinish in which variously colored enamels are applied successively and fired after the application of each color. Under this practice', the repetitive firing tends to develop surface defects or to from the group consisting of iron, cobalt and l manganese, -applying a vitrecius enamel on the alloy layer, ring the base to fuse the enamel, applying a second enamel of contrasting color on portions of the fused enamel, and -rering the base to mature the second enamel.

June 8,

(Cl. 2li-8,8) y

base l is formed from grades of iron or steel are suitable for this purpose and the material is selected primarily onV v the basis of cost and formability. A

5 After Ithe ring-shaped base is formed, it is cleaned by the usual methods and then completely coated with a layer of copper Il. The copper can be applied conveniently in a conventional copper-cyanide electroplating 'process and a coating weight around 20 milligrams per square linch is generally satisfactory.

In the next operation an alloy Il is applied over the copper in a uniformlayer. Three types of alloy are suitable and good results are obtained l5 by alloying nickel with iron, 'or cobalt, or man- Ii a nickel-iron alloy is used, the iron content ance nickel and the best results are secured with an alloy having aniron content around 1.50%. This optimum composition can be obtained from an aqueous electroplating bath containing the following ingredients and operated under the following conditions:

composition of bain Ounces per gallon of solution Nikel Sulphate Sodium chloride. 3.0v y 30 Borlc acid l l 4.0 Ferrous sulphate .0666

sumcient siupnunc acid is added to keep tile solution-in a slightly acid condition, a pH of 5 being satisfactory. The process is operated cold 'at a current density around 10 amperes per square foot of cathode surface, Since a variation oi this current density will affect the proportions of iron in the deposited alloy for the given solution and temperature, it is necessary to consider this interrelation of current density and alloy composition ating temperatures. The ferrous sulphate can be added as such to initiate the process and then maintained by placing pure iron anodes in parallel with pure nickel anodes in the bath.

Y It the nickel is alloyed with cobalt, Va. cobalt content between 1.0% and 15.0% is operable and a cobalt content of 5.0% is preferred. If a nickelmanganese alloy is employed,.the manganese percentage is held between .20% to 5.0%, and 1.0% manganese is optimum. The nickel-cobalt and nickel-manganese alloys can be electrodeposited on the copper in a. plating 'bath containing appropriate salts and anodes of the respective metals,

sheet-metal. Various should be between .50% and 10.0% with the bal- -for dinerent solution concentrations andoperoorrespo to the elements employed for-elecas clay.

' insubsequent printing operations.

. order to minimize the cost of the article and also to facilitate the maintenance of over-all dimensional tolerances.

A coating vof white enamel I8, such as a lead boro-silicate enamel opaciiied with arsenic oxide, isapplied first: The enamel is distributed'onthe alloysurl'acel either in the form of dry Powder or by a' wet process in which the enamel particles are mixed with water and a flotation agent, such The base 'is then red at 1600o F. for four and one-half minutes to fuse the enamel. Identifying characters in contrasting colors are usually required to complete the plate. One type of plate, shown in the drawing, has a background Il, letters l and numerals I8. These characters are produced with an inkysuspension of colored metallic oxides or frits in a vehicle such as linseed oil and are applied on the surface of the white enamel by a printing operation. The back-A ground, which may be blue or black, is applied first and the plate is then baked at about 300 F. to harden the ink so that it will not be marred The letters. which are usually black, are then applied and the plate is then again baked at a temperature of about 300` F. The numeralsare usually colored red and are applied in the same manner, after which the entire plate lis again red to fully mature the ceramic ink which requires a tempitting of the enamel is a serious source of trouble. The occurrenceof very small pits is not easily detected when the plates are new, but after a periodof service, dirt and other foreign particles tend to accumulate and become imbedded in the pits to form smudges. These smudges are very diillcult to remove, particularly because the any reiiring operations and are reiiected in all -portions of the completed enamel coating. For

most applications, a coating weight of 20 milligrams per 4square inch for both the copper and the alloy is satisfactory. It may be desirable to -vary these values somewhat for diileren't enamel compositions and, in general, the copper and alloy layers should be of about equal weight.

The combination of copper and alloy layers also adequatelyprotects the portions of the base that are not covered with enamel against atmosphere corrosions.

Although the invention has been described in connection with the manufacture of number plates for telephone dials, it will be apparent that ,it is equally applicable to other ornamented en- `manganese alloy comprising from .20% to 5.0%

manganese and the balance nickel on the copper, and a coating of vitreous enamel on the alloy.

`. 3. A method of forming an enamel coated article which comprises copper plating a ferrous metal base, lectrodepositing an alloy of from .201% to 5.0% manganese and the balance nickel on the copper plate, and Aapplying a vitreous coating over the alloy plate.

4. An enamel coated article comprising an iron base, acopper plated coating of around 20 milligrams per square inch thereover, a layer of nickel-manganese alloy over the copper plate. saidv alloy comprising from .2% to 5.0% manganese and the balance nickel and being substantially the same thickness as the c opper plate, and a fused enamel coating over the nickel-manganese alloy.

5. In a method of forming an article, the steps of electrodepositing a copper coating on a ferrolls metal base, electrodepositing a nickel-manganese alloy comprising 1% manganese and the balance nickel on the copper, applying a vitreous enamel to the coated base, and ring the article to fuse the enamel and form an enameled coating.

` MORRIS BROWN.

RUSSEL E. HARR. 

